Fundamental Technologies

Galileo Spacecraft Pages

Appendix E. EPD File Structure (continued)

2. Record Header

Source: T. P. Armstrong, March 30, 1985

Galileo EPD Record Header Definition

This header block will be present in all EPD records.

ItemDescription Type Length
0 Spacecraft Name
  Value Meaning
  'ISPM'International Solar Polar
A*4 4
1 Record Descriptor
  'EPDH'File Header Record
  'HHSS'Housekeeping and Status Record
  'LMPA'LEMMS Pulse Height Analysis Record
  'PHAR'Pulse Height Archive
  'RATE'Rate Block
A*4 4
2Production Date
"DD-MMM-YY" Creation Date
A*10 10
3 File Type
  "AV"=EPD Average
  "AR"=EPD Archive
A*2 2
4Procedure Name A*6 6
5Procedure Version I*2 2
6 Time of First Data Occurrence
  Array #Description
I*2 10
7Time of Last Data Occurrence
(see expl. of item #6)
I*2 10
8Instrument Status Block (report of voltages, temperatures, and digital status flags) I*4 TBD
9 Magnetic Field Data
  Coordinates: Payload
  First Index: Labels up to 64 repetitions of magnetic field data in each record. This is included to give maximum time resolution in subsequent pitch and phase angle calculations as per the request of DJW 4/24/84.

  Second Index:

# samples
R*4 6
10 Ephemeris Block

Heliocentric Inertial Cartesian States (x, y, z, vx, vy, vz--km & km/sec) of:
   a.) Spacecraft
   b.) Earth
   c.) Jupiter

Jovicentric Mean Orbit Cartesian States (x, y, z, vx, vy, vz--km & km/sec) of:
   d.) Spacecraft
   e.) Io
   f.) Europa
   g.) Ganymede
   h.) Callisto

Jovicentric Magnetic Axis System III Spherical Coordinates (r, theta, phi) of:
   i.) Spacecraft
   j.) Io
   k.) Europa
   l.) Ganymede
   m.) Callisto

11Orientation Block
 Transformations from:
   a.) Payload to SCC. (SCC--spacecraft centered corotation)
   b.) Payload to Heliocentric
   c.) Payload to System III
   d.) Payload to Inertial
   e.) Payload to B field
12Sector Block

 THETA(60,8,2) Polar angle of 60 sectors in 8 steps
 for B field coords. (1) and SCC (2)
 PHI(60,8,2) Azimuth angle of 60 sectors in 8 steps
 for B field coords. (1) and SCC (2)
 BMAG(60,8) Magnitude of B field for 60 sectors and 8 steps

13 Stepping Block
    Variable: ISTEP(12)
     Type: I*4
     Index Contents
1Step position for this record (0-7)
2Step position for former record (0-7)
3Next expected step position (0-7)
4Position expected in next record (0-7)
5Direction of step movement:
   +1 = increasing
   0 = this record is from a turn
   -1 = decreasing
6Minimum sector of scan (0-7)
7Maximum sector of scan (0-7)
8Dwell time (milliseconds) per step
9Slew rate (millidegrees/second)
14Spares -- TBD
15Number of Physical Records in this Logical Record I*2 2
16Index of this Physical Record

Explanation of items 15 and 16:  For record types of length small enough to fit into the fixed (defined) number of bytes for an EPD record, the blocking factor will be 1:1. That is, item #14 = 1 and item #15 = 1. For large logical records which would necessarily span several physical records, item #14 gives the blocking factor, say 8 for 8:1, and item #15 tells which of the 8 possible records this one is.

I*2 2

Next: 3. Rate Block

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Updated 10/12/04, T. Hunt-Ward